This invention relates to hand held pneumatic tools of the type commonly used as demolition hammers.
It is well known to provide a pneumatic tool for use as a demolition hammer, which tool comprises a body forming a cylinder and having a handle at an upper end and a tool receptacle at a lower end, a piston being reciprocable within the cylinder under the action of compressed air so as to strike the tool repetitively. The operator holds the tool with both hands, one hand being on the top handle and the other hand on the body of the tool.
Known tools of this nature impose a high degree of vibration upon the operator. In recent times there has been increasing concern as to the risk to health which such vibration poses, and current health and safety regulations in the United Kingdom are now planned which will try to reduce vibration levels to which operators of such tools may be exposed. There is accordingly a need for a tool of this type which imposes significantly lower vibration upon the operator""s hands.
Accordingly, the present invention provides a hand held pneumatic tool comprising a body which includes a cylinder, a tool holder at a lower end of the body, a handle at an upper end of the body, a piston reciprocable within the cylinder between a lower position in which it strikes a tool in the tool holder and an upper position, an inlet for receiving compressed air, and a first valve means interposed between the inlet and the cylinder so as to cause the piston to reciprocate within the cylinder; and in which the handle is connected to the body by a resilient connection means which permits relative axial movement between the handle and the body; and a hand grip is provided around the body at a location spaced from the handle, the hand grip being connected to the handle for movement therewith.
Preferably, the hand grip is formed integrally with a muffler through which exhaust air from the tool passes.
In one form of the invention, said first valve means is secured to the handle for movement therewith. In an alternative form, said first valve means is secured to the body.
Preferably, the resilient connection means comprises a plurality of guide posts (which may be provided by shouldered bolts) and spring means which may suitably comprise respective coil springs around one or more of said posts.
In a preferred embodiment, the tool further includes flow control means for varying the supply of compressed air from the inlet into the cylinder.
Preferably, said flow control means comprises a second valve means located between the inlet for receiving compressed air and the first valve means.
Preferably, said flow control means is adapted to vary the extent of opening of an air passage connecting said inlet to said first valve means.
Preferably, said flow control means is adapted to vary the compressed air supply in a plurality of discrete steps.